# From a lift moving upwards with a uniform acceleration a = 2ms-2, a man throws a ball vertically upwards …..

Q. From a lift moving upwards with a uniform acceleration a = 2ms-2, a man throws a ball vertically upwards with a velocity v = 12 ms-1 relative to the lift. The ball comes back to the man after a time t. Find the value of t in second (g=10ms-2).

(a) 4

(b) 2

(c)5

(d) 6

Ans: (b)
Sol:
Time taken by ball to come back to the man is

$\displaystyle t = \frac{2v}{g+a}$

$\displaystyle t = \frac{2\times 12}{10+2}$

t = 2 sec

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